The publication by M. Valant and D. Suvorov, “Microwave Ceramics with Permittivity over 400,” The 9th International Meeting on Ferroelectricity, Seoul, South Korea, 1997, Abstract Book, P-05-TH-067 discloses multilayer capacitors whose dielectric layers comprise a ceramic material based on a niobium-based perovskite-like solid solution having the general formula A(B1−xNbx)O3. It was found that ceramics of this type are characterized by a high relative permittivity ε>400. Furthermore, at low frequencies between 100 kHz and 1 MHz, these ceramic materials have dielectric properties that make them suitable for use in multilayer capacitors.
A ceramic material is known from the publication by A. Kania, “Ag(Nb1−xTax)O3Solid Solutions—Dielectric Properties and Phase Transitions,” Phase Transitions, 1983, Volume 3, pp. 131–140, produced from silver, niobium and tantalum, referred to here as ANT, which exists in the form of a solid solution of the two materials AgNbO3 and AgTaO3. The ceramic described in this publication comprises the composition Ag(Nb1−xTax)O3, referred to here as ANTx, wherein x can vary from 0 to 0.7. Depending on the composition, at a temperature of approximately 300 K, the ceramic has an ε of between 800 and 400.
From the publication by Matjaz Valant and Danilo Suvorov, “New High Permittivity Ag(Nb1−xTax)O3 Microwave Ceramics: Part 2, Dielectric Characteristics,” J. Am. Ceram. Soc. 82 (1), pp. 88–93 (1999), it is known that disk-shaped ceramic bodies made of ANTx with an x parameter between 0.46 and 0.54, exhibit a strong relative change in the relative permittivity ε in the temperature range between −20° C. and 120° C. It was demonstrated in particular that the relative change of ε with varying temperature describes a curve that reaches a maximum between 20° C. and 70° C., and assumes values between −0.07 and 0.01.
It is further known from publication WO 98/03446 that by adding lithium, wolfram, manganese or bismuth to ANT, in the case of individual temperatures, the temperature coefficient of the relative permittivity TKε can be reduced to very small values as low as ±−70 ppm/K.
Although the known ANT materials have a high ε, they have the disadvantage of having relatively high TKε values in the temperature range between −20° C. and 80° C. that is of interest for applications. At the same time, a high temperature coefficient of relative permittivity εresults in a high temperature coefficient of the capacitor's capacitance.